What effect does the melt index of a resin have on its ability to ...

[BrownTown3]

What effect does the melt index of a resin have on its ability to be rotationally molded? When (give two examples of parts or applications) would you want to use a higher melt index resin? When (give two examples) would a low melt index resin be desired? Explain.
 
  What will be an ideal response?

Question 2

Name and discuss in some detail three process/ machine considerations when injection molding a whisker-reinforced part. Think about the fiber length, the small clearances between the nozzle and part, flow through the part, type of resin (i.e. thermoplastic vs. thermoset), Screw speed, etc are some of the considerations that could be discussed somewhere in their answer. Define symmetry and balance as they relate to composite lay-ups, and give examples of having one but not both qualities. What will happen to the part if both are not met?
 
  What will be an ideal response?

[nathang24]

Answer to Question 1

When the material has a low melt index it indicates that the material is of high molecular weight. This high weight does not enable the material to flow well through the mold and requires a higher temperature and longer cycle time for the

machine. Two examples that would require a lower melt index would be a truck bed or the TYCO children's playgrounds that would have to withstand greater pressures and weights.

A higher melt index for a rotomold would allow the material to flow better and reach deep crevices, lower temperatures and lessen the cycle time of parts. Two examples of this type of application would be a cheap bouncy ball or a bathtub rubber ducky that would require a squeeker later.

Answer to Question 2

Symmetry is when the part is cut directly down the middle the two sides are mirror images of each other. Balance is determined by the angles that the direction of the fibers are going in and making sure that they cancel each other out. If these factors are not met in the part layup there will be warpage in the part's structure. If both are met the maximum strength that the fibers can give is met.

[BrownTown3]

Thanks

[nathang24]

Welcome